Polycyclic hydrocarbon‐produced toxicity, transformation, and chromosomal aberrations as a function of aryl hydrocarbon hydroxylase activity in cell cultures

The cytotoxic effect of benzo[a]pyrene alone in fetal rat hepatocytes in culture is prevented by phenobarbital. Benzo[a]pyrene is not toxic to HTC, A9, or HeLa cells in which aryl hydrocarbon hydroxylase activity is either absent or very low; however, benzo[a]pyrene is cytotoxic to each of these three established cell lines grown together with the liver cells in the presence of phenobarbital. Polycyclic hydrocarbon‐produced cytotoxicity is associated with chromatid breaks, whereas aneuploidy is more closely correlated with malignant transformation of hamster secondary cultures. Benz[a]anthracene or a‐naphthoflavone competitively inhibits the hydroxylation of other polycyclic hydrocarbons such as the carcinogens 7,12‐dimethylbenz[a]anthracene or benzo[a]pyrene. The exposure of fetal hamster secondary cells to excessive amounts of benz[a]anthracene prior to, during, and following treatment with 7,12‐dimethylbenz[a]anthracene prevents malignant cell transformation from occurring.